1. The Field of the Invention
The present invention generally relates to interfacing two different content protection schemes. More particularly, the present invention provides producing a digital rights management license for consuming protected content that originated from a conditional access scheme, while maintaining security of the content and any associated content protection information.
2. Background and Related Art
Growing concerns over the distribution of copyrighted content (such as audio, video, text, data, multi-media, etc.) over a wide range of media (e.g. magnetic disks, magnetic tape, optical disk, satellite, cable, terrestrial, etc.) has led to a number of diverse content protection methods. Generally these schemes are designed to protect content during transit as well as after the content has been received (e.g. at a set top box, personal computer, television, mobile phone, etc.). Two common types of protection schemes include conditional access (CA) and digital rights management (DRM) systems.
Conditional access (CA) systems (which are described in greater detail below, for example, with regard to FIGS. 2 and 3) are used in broadcast platforms to securely deliver content from a service operator, such as a satellite or cable provider, to individual receivers. Most network operators will scramble at least some of their services in order to protect their pay-TV operations. Conditional access systems utilize security principles that include the encrypted data as well as two additional types of data known as CA messages (CAM), which are typically broadcast in the transport stream along with, or in parallel with, the scrambled program. CAMs consist of two separate and independent messages streams, one that includes a set of intermittent and continually updated encryption keys and the other that includes the subscriber rights to view a specific program. Both CA messages include the associated access conditions.
In contrast to CA systems for broadcast delivery of content (and as described in greater detail below, for example, with regard to FIGS. 2 and 3), DRM systems have been developed to securely allow consumption of other types of content (e.g., CDs, MPEG files, DVDs, audio/video streams, etc.) on devices such as personal computers and other electronic items. Rather than the multitude of intermittently updated keys and the multiple message streams used in CA schemes, DRM systems typically use a single license that includes the content usage rights as well as a decryption key for consuming the protected content. Further, the license can be delivered independent of the content, yet bind the content to the license and to a particular device or potentially a group of devices.
CA and DRM technologies were developed for protecting different types of content with different delivery mechanisms, and thus with different security risks in mind. For example, CA protection systems were developed for pay-TV media that is broadcast of to a plurality of devices in a streaming fashion, i.e., real time playback. Accordingly, because the content is broadcast and streamed, the various levels of protection (such as the intermittent updated keys and encryption thereof at different times and concealed in different messages) were considered important, possible, and practical.
On the other hand, DRM systems were developed for sending a single piece of content (i.e., not necessarily a real time broadcast, but digital data that can be stored and subsequently played/consumed) to typically a single device (or small group of devices). Accordingly, the binding of the content to a single license and binding the license to a particular device (or group of devices) provides an appropriate level of protection which is somewhat tailored to how the content is received and consumed.
Emerging network technology, e.g. home networking, however, is beginning to expose current incompatibilities between these alternative content protection methods. In particular, the desire to make all (or at least most) appliances and other devices within a home capable of communicating with one another, and being able to utilize the unique capabilities of each devices on any device within the home network, make unifying these two content protection systems advantageous.